Simplify class symbol check for OnlyCapability

Author: noti0na1

compiler/src/dotty/tools/dotc/cc/CaptureOps.scala

@@ -922,11 +922,8 @@ object OnlyCapability:
 
   def unapply(tree: AnnotatedType)(using Context): Option[(Type, ClassSymbol)] = tree match
     case AnnotatedType(parent: Type, ann) if ann.hasSymbol(defn.OnlyCapabilityAnnot) =>
-      ann.tree.tpe.argTypes.head.dealias match
-        case tp: TypeRef if tp.symbol.isClass =>
-          tp.symbol match
-            case cls: ClassSymbol => Some((parent, cls))
-            case _ => None
+      ann.tree.tpe.argTypes.head.dealias.typeSymbol match
+        case cls: ClassSymbol => Some((parent, cls))
         case _ => None
     case _ => None
 end OnlyCapability